JPH0952169A - Refractory for tuyere of molten steel container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refractory for a tuyere containing carbon to prevent wear due to oxygen cleaning. SOLUTION: A refractory 3 for a tuyere of a molten steel container is obtained by the flowed-in forming of the mixture having the composition consisting of, by weight, 100% refractory aggregate which is mainly composed of 80-90% alumina of <10mm in grain size and 3-20% magnesia of <=75μm in grain size, 1-10% hydraulic alumina, 0.05-5% amorphous silica supper-fine powder, and 1-7% metallic fiber, which are applied to 100% the refractory aggregate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory for tuyere in a molten steel container.

[0002]

2. Description of the Related Art A casting nozzle for pouring molten steel or a porous plug for stirring molten steel is provided at the bottom of a molten steel container. When these nozzles or plugs are reused, they are removed by oxygen cleaning when they are reused. This is because the casting nozzle is used to open the nozzle hole, and the porous plug is used to restore the gas permeation function.

FIG. 1 shows the situation of oxygen cleaning, taking the case of a porous plug as an example. (1) is a refractory lining at the bottom, (2) is a porous plug, (3) is a refractory for tuyere located around it, (4) is a bare metal, and (5) is an oxygen nozzle. The metal is heated by blowing oxygen during heat retention and is dissolved and removed. Although not shown in the figure, the same operation is performed in the case of oxygen cleaning of the casting nozzle.

[0004]

The refractory material for tuyere is significantly worn out by erosion due to molten metal and thermal shock during oxygen cleaning. Further, as a result of the oxygen cleaning weakening the refractory structure, the melt loss is accelerated by the high-speed molten steel flow received at the time of use in the casting nozzle and the turbulent flow of molten steel by the stirring gas in the porous plug.

Conventionally, as a material for this refractory material for tuyere, Japanese Unexamined Patent Publication (Kokai) No. 5-8020 proposes an unfired magnesia-carbonaceous refractory material. This material is excellent in corrosion resistance and spalling resistance against molten steel, but the refractory structure becomes fragile due to the oxidation of carbon components received during oxygen cleaning, and sufficient durability cannot be obtained.

The casting nozzle is filled with a filling material in order to prevent the molten steel from solidifying in the nozzle hole until the molten steel is poured out. Carbon-containing tuyere refractory has a high thermal conductivity, so this filling tends to cause burning,
There is also a problem that it becomes difficult for the filling material to flow off when the molten steel pouring is started.

In addition, since the tuyere refractory is a large-sized deformed refractory, the press molding method has problems such as high manufacturing equipment cost and increased manufacturing man-hours.
Therefore, it has been attempted to use a refractory for a tuyere that is cast by casting an amorphous refractory that does not contain carbon. However, the wear resistance during oxygen cleaning is still insufficient. It is an object of the present invention to provide a refractory material for tuyere that solves the above-mentioned conventional drawbacks.

[0008]

The gist of the present invention is as follows. 1. 80-97 wt% alumina having a particle size of less than 10 mm,
100 wt% of refractory aggregate mainly composed of 3 to 20 wt% of magnesia having a particle size of 75 μm or less, hydraulic alumina of 1 to 10 wt% by external coating, amorphous silica ultrafine powder of 0.05 to 5 w
A refractory for a molten steel container tuyere obtained by casting a mixture containing t% and 1 to 7 wt% of metal fibers.

[0009] 2. Alumina with a particle size of less than 10 mm 80 ~
97 wt%, magnesia 3 to 20 with a particle size of 75 μm or less
100% by weight of a refractory aggregate whose main content is 10% by weight or less of magnesia having a particle diameter of more than 75 μm and less than 10 mm, and 3 to 20% by weight of magnesia of 75 μm or less and magnesia of more than 75 μm and less than 10 mm. , Hydraulic alumina 1-10 wt% on the outside, amorphous silica ultrafine powder 0.05-5 wt% and metal fiber 1-7w
A refractory for a molten steel container tuyere obtained by casting a compound containing t%.

3. In the refractory for the tuyere of the molten steel container, the content of the alumina cement was 3 wt% or less with respect to 100 wt% of the refractory aggregate, and the total amount of hydraulic alumina and alumina cement was 1 to 10 wt%.

4. In the refractory for a tuyere of a molten steel container, 40 wt% or less of a refractory coarse particle having a particle diameter of 10 mm or more was externally added to 100 wt% of a refractory aggregate.
The hydraulic alumina used as the binder in the present invention is
It is mainly composed of ρ-alumina and has an intermediate crystal structure between aluminum hydroxide and α-alumina. Actually, in the manufacturing process, other γ-alumina is inevitably used.
It contains less than 50 wt% of other alumina such as χ-alumina.

The hydraulic alumina used in the present invention causes rehydration with water added at the time of casting to develop the bond strength of the refractory structure. Moreover, unlike alumina cement that is generally used in casting, it does not contain CaO and thus has excellent resistance to FeO.

Alumina-spinel or alumina-
When the magnesia casting material contains CaO, it reacts with FeO during the cleaning with oxygen, so that 4CaO · Al ₂ O ₃ ·.
This produces Fe ₂ O ₃ (melting point 1415 ° C.). 4CaO ・ A
l ₂ O ₃ · Fe ₂ O ₃ has a eutectic point with MgO · Al ₂ O ₃ which is a refractory component, and the melting point decreases to 1320 ° C., the amount of liquid phase generated increases, and melting loss occurs. Be promoted.

In the present invention, the use of CaO-free hydraulic alumina does not produce CaO-based low-melting-point substances.
Since eO forms a solid solution in MgO.Al ₂ O ₃ , the melting point is not significantly lowered. As a result, the refractory for tuyere according to the present invention prevents the refractory structure from becoming weak during oxygen cleaning.

In the present invention, hydraulic alumina easily forms spinel by reaction with fine powder of magnesia, makes the refractory structure a strong spinel bond structure, and prevents weakening of the refractory structure during oxygen cleaning. Greatly affects. It is considered that this is because the crystal structure of ρ-alumina, which is the main component of hydraulic alumina, is more unstable than that of α-alumina, which is a normal alumina crystal structure, and the spinel reaction is likely to occur.

The compound used in the present invention will be described in detail below. Alumina is a material having both corrosion resistance and volume stability, and has a role as a main aggregate in the present invention. Either a sintered product or an electromelted product can be used. Al ₂ O ₃
The purity is preferably 90 wt% or more. TiO ₂ less than 5 w
Those containing t% can also be used. In addition, low-purity products such as sand shale, sillimanite, and mullite may be used, but it is preferable to use high-purity products in the fine powder portion.

The particle size of alumina is less than 10 mm in order to distinguish it from the refractory ultra-coarse particles described later, but it is preferably 7 mm or less. In order to obtain a close-packed structure, the grain size is adjusted to coarse grains, medium grains, and fine grains within this range before use. A calcined product may be used as the fine powder.

The magnesia may be either a sintered product or an electromelted product. Magnesia itself has excellent resistance to slag erosion and, in addition to MgO.Al ₂
O ₃ -based spinel is generated, and this spinel forms a solid solution with components such as FeO and MnO in the slag, and thus has the effect of preventing slag penetration into the refractory structure.

Magnesia is composed of 3 fine powders having a particle size of 75 μm.
˜20 wt%. If it is less than 3 wt%, the spinel formation is insufficient, so that the slag penetration preventing effect is not exhibited. Two
If it exceeds 0 wt%, the amount of spinel produced becomes excessive,
The refractory structure deteriorates due to volume expansion associated with spinel formation.

In view of particle size constitution, if necessary, magnesia having a particle size of more than 75 μm and less than 10 mm may be added in addition to the fine powder of magnesia. However, the ratio is set to 10 wt% or less due to the particle size configuration. The particle size is 75
The total amount of magnesia having a diameter of more than 10 μm and less than 10 mm and the above-mentioned fine powder magnesia is 3 to 20 wt%.

The hydraulic alumina used as the binder is
It has an intermediate crystal structure between aluminum hydroxide and α-alumina. ρ-alumina is the main component,
In addition, it is a mixture containing γ-alumina, χ-alumina and the like. It is preferable that the average particle diameter is 1 to 20 μm and Al ₂ O ₃ : 99% or more. This hydraulic alumina can be obtained from a commercially available product. If the ratio is less than 1 wt% when applied to 100 wt% of refractory aggregate, the strength of the work body is poor, and if it exceeds 10 wt%, there is a problem of deterioration in workability such as poor flowability during casting.

The hydraulic alumina may have a slower hardening when the curing temperature is low such as in winter. Therefore, alumina cement may be used as a curing accelerator. However, if the proportion of alumina cement exceeds 3 wt%,
The CaO in the alumina cement lowers the FeO resistance, and the effect of the present invention cannot be obtained.

As the amorphous silica ultrafine powder, for example, volatile silica commercially available under the trade name such as silka flour or micro silica, which is obtained as a by-product in the production of silicon or a silicon alloy, can be used. The ultrafine particles have a specific surface area of about 15 to 50 m ² / g.

The use of magnesia has a problem that it causes dry cracks due to volume expansion due to its hydration reaction. The ultrafine amorphous silica powder has the effect of preventing hydration of magnesia by reacting with magnesia and covering the surface with hydrous silicate of magnesia.

The ratio of amorphous silica ultrafine powder is 0.05 w
If it is less than t%, there is no effect of preventing hydration, and if it exceeds 5% by weight, it is a low-melting substance such as 2MgO.2Al ₂ O ₃ .5SiO.
₂ (melting point 1460 ° C.) is formed and corrosion resistance is lowered.

The metal fiber has an effect of spalling resistance. The specific material is preferably stainless steel in terms of heat resistance, but iron, carbon steel, Ni-Cr steel, A
1, Al alloy, etc. may be used. The shape may be straight or curved. In addition, the diameter is 0.1-2m.
It is preferable that the length m is about 5 to 50 times the diameter (for example, 5 to 40 mm). The ratio of addition is 1 out of 100 wt% of refractory aggregate.
If it is less than wt%, there is no effect of spalling resistance, and it is 7 wt.
When it exceeds%, the workability is deteriorated such that the kneading is not easy.

As the refractory ultra-coarse particles, for example, alumina and spinel can be used. Alumina super coarse particles have an effect of spalling resistance when used in combination with ultra fine magnesia powder. If the particle size is less than 10 mm, the effect of spalling resistance is poor. If the particle size exceeds 50 mm or if the ratio exceeds 40 wt% on the outside, the strength of the construction body is deteriorated due to the imbalance of the particle size composition, and the corrosion resistance is deteriorated.

The specific material of the ultra-coarse particles of alumina is
Either an electro-melted product or a sintered product may be used. Brick scrap containing alumina as a main component may be used. In addition, MgO.Al ₂ O ₃ spinel is superior to alumina in corrosion resistance, and when used under conditions where importance is attached to corrosion resistance, some or all of the alumina-based coarse particles have a MgO / Al ₂ O ₃ spinel content higher than that of alumina. It is preferable to use coarse particles.

In order to adjust workability, pot life and the like at the time of casting, a peptizer, a curing modifier and the like are usually added in an amount of about 0.01 to 0.5 wt%. Specific examples of the deflocculating agent include, for example, sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, acidic sodium hexametaphosphate, sodium borate, inorganic salts such as sodium carbonate, sodium citrate, sodium tartrate, sodium polyacrylate. , Sodium sulfonate, etc. Examples of the curing modifier are boric acid, ammonium borate, ultrapolyphosphate sodium carbonate, lithium carbonate and the like.

If necessary, metal powder (for example, aluminum powder,
Aluminum alloy powder, etc.), glass powder, carbon powder, pitch powder, zircon, zirconia, organic fiber, ceramic fiber, foaming agent and the like may be added.

As for the casting, as in a conventional method, about 4 to 8% by weight of water is added and mixed by externally adding to the above-mentioned composition, and the mixture is poured into a mold. In that case, in order to improve the filling property, it is preferable to attach a vibrator to the mold or insert a rod-shaped vibrator into the refractory.

[0032]

EXAMPLES Examples of the present invention and comparative examples will be shown below.
Table 1 shows the composition of the refractories for tuyere of each example and the test results thereof.

[0033]

[Table 1]

In each of the examples, the formulation shown in Table 1 was externally applied to 5% by weight of construction water and 0.1% of a dispersant (sodium polyacrylate).
After adding wt% and kneading, the mixture was poured into a mold to which vibration was applied, and after curing, the frame was removed and dried at 110 ° C. for 24 hours. The test method is as follows.

Bending strength: measured after drying at 110 ° C. and after heating at 1500 ° C. Corrosion resistance: A weight ratio of steel slab: converter slag = 1: 1 was used as an erosion agent, and a rotary erosion test was performed at 1650 ° C. for 4 hours to measure a melt loss size and a slag infiltration size.

Oxygen cleaning resistance: Molten steel-oxygen was sprayed onto a sample heated in a rotary erosion furnace using a pickling rod, and the melt loss size and slag permeation size after the test were measured. In the examples of the present invention, good results were obtained in any of the tests of corrosion resistance, slag penetration resistance and oxygen cleaning resistance.

On the other hand, Comparative Examples 1 and 2 using only conventional alumina cement and Comparative Example 3 containing a large amount of alumina cement are inferior in oxygen cleaning resistance. In Comparative Example 4 in which the amount of hydraulic alumina added is small, sufficient strength cannot be obtained after drying. Comparative Example 5 containing a large amount of hydraulic alumina has poor fluidity and poor workability. In Comparative Example 6 in which the amount of magnesia added was large, the refractory structure was deteriorated due to the volume expansion accompanying the spinel reaction, and the oxygen cleaning resistance was poor. Comparative Example 7 containing a large amount of the amorphous silica ultrafine powder is inferior in corrosion resistance and oxygen cleaning resistance due to the formation of the low melting point substance.

[0038]

As described above, according to the present invention, in the alumina-magnesia refractory material for tuyere, by using hydraulic alumina instead of alumina cement, the corrosion resistance originally possessed by the alumina-magnesia material can be obtained. In addition, FeO resistance can be imparted, and it becomes possible to provide a tuyere refractory having a high oxygen cleaning resistance.

[Brief description of drawings]

FIG. 1 shows a situation of oxygen cleaning.

[Explanation of symbols]

 1 Bottom lined refractory 2 Porous plug 3 Tuyere refractory 4 Bare metal 5 Oxygen nozzle

Claims (4)

[Claims] 1. Alumina 80-97 having a particle size of less than 10 mm.
3% to 20% by weight of magnesia with a particle size of 75 μm or less
% As the main material, 100 wt% of refractory aggregate, 1-10 wt% of hydraulic alumina by external coating, ultrafine amorphous silica powder 0.0
A refractory for a molten steel container tuyere obtained by casting a mixture containing 5 to 5 wt% and metal fibers of 1 to 7 wt%. 2. Alumina 80-97 having a particle size of less than 10 mm.
3% to 20% by weight of magnesia with a particle size of 75 μm or less
%, Magnesia with a particle size of more than 75 μm and less than 10 mm 1
The main material is 0 wt% or less, and the total amount of the magnesia of 75 μm or less and the magnesia of more than 75 μm and less than 10 mm is 3 to 20 wt%, and 100 wt% of the refractory aggregate, and 1 to 10 wt% of the hydraulic alumina is externally applied. Amorphous silica ultrafine powder 0.05-5 wt% and metal fiber 1-7 wt%
A refractory for a molten steel container tuyere obtained by casting a mixture containing 3. The tuyere of the molten steel container according to claim 1, wherein the content of the alumina cement is 3 wt% or less with respect to 100 wt% of the refractory aggregate, and the total amount of hydraulic alumina and alumina cement is 1 to 10 wt%. Refractory. 4. A particle size of 10 m with respect to 100 wt% of refractory aggregate.
The refractory material for a tuyere of a molten steel container according to claim 1 or 2, which contains 40 wt% or less of coarse refractory coarse particles of m or more.